Functional silane-compatibilized epoxy compositions for insulation applications

Abstract

Described is an epoxy composition containing: (a) an epoxy resin containing at least one epoxy group, (b) an anhydride hardener, (c) a hydroxyl-terminated polysiloxane, and (d) a functional silane having at least one functional group selected from the group consisting of an epoxy-reactive group, an anhydride-reactive group, and an epoxy- and anhydride-reactive group. Also describing a crosslinked epoxy composition and a method for preparing thereof.

The invention claimed is: 
     
       1. An epoxy composition comprising:
 (a) an epoxy resin containing at least one epoxy group, 
 (b) an anhydride hardener, 
 (c) a hydroxyl-terminated polysiloxane, and 
 (d) a functional silane having at least one functional group selected from the group consisting of an epoxy-reactive group, an anhydride-reactive group, and an epoxy- and anhydride-reactive group, wherein molar ratio of the functional group of the functional silane to the epoxy group of the epoxy resin (a) is less than 0.25; 
 wherein molar ratio of total hydroxyl group(s) in the hydroxyl-terminated polysiloxane to total alkoxy group(s) in the functional silane is 3.5 or less. 
 
     
     
       2. The epoxy composition of  claim 1 , wherein the epoxy resin is a cycloaliphatic epoxy resin. 
     
     
       3. The epoxy composition of  claim 1 , wherein the molar ratio of total hydroxyl group(s) in the hydroxyl-terminated polysiloxane to total alkoxy group(s) in the functional silane is from 0.001 to 1.5. 
     
     
       4. The epoxy composition of  claim 1 , wherein the functional silane is selected from an aminosilane and an epoxy silane. 
     
     
       5. The epoxy composition of  claim 1 , wherein the hydroxyl-terminated polysiloxane is hydroxyl-terminated polydimethylsiloxane. 
     
     
       6. The epoxy composition of  claim 1 , wherein the content of the hydroxyl-terminated polysiloxane is from 0.5 to 25 weight-percent based on the weight of the epoxy resin. 
     
     
       7. The epoxy composition of  claim 1 , wherein molecular weight of the hydroxyl-terminated polysiloxane is from 400 grams per mole to 70,000 grams per mole. 
     
     
       8. The epoxy composition of  claim 1  further comprising a cyclic polysiloxane. 
     
     
       9. The epoxy composition of  claim 8 , wherein the content of the cyclic polysiloxane is from one to 3 weight-percent, based on the epoxy resin weight. 
     
     
       10. A crosslinked epoxy composition obtained by curing the epoxy composition of any of  claims 1 - 9 . 
     
     
       11. A method for preparing the epoxy composition of  claim 1 , comprising steps of mixing
 (a) an epoxy resin containing at least one epoxy group, 
 (b) an anhydride hardener, 
 (c) a hydroxyl-terminated polysiloxane, and 
 (d) a functional silane having at least one functional group selected from the group consisting of an epoxy-reactive group, an anhydride-reactive group, and an epoxy- and anhydride-reactive group, wherein molar ratio of the functional group of the functional silane to the epoxy group of the epoxy resin (a) is less than 0.25; 
 wherein molar ratio of total hydroxyl group(s) in the hydroxyl-terminated polysiloxane to total alkoxy group(s) in the functional silane is 3.5 or less. 
 
     
     
       12. The method of  claim 11 , wherein the anhydride hardener, the hydroxyl-terminated polysiloxane and the functional silane are mixed to react first, before mixing with the epoxy resin. 
     
     
       13. The method of  claim 11 , wherein the epoxy resin, the hydroxyl-terminated polysiloxane and the functional silane are mixed to react first, before mixing with the anhydride hardener. 
     
     
       14. The method of  claim 13 , wherein the epoxy resin reacts with the functional silane having at least one epoxy-reactive group or at least one epoxy- and anhydride-reactive group first, before mixing with the hydroxyl-terminated polysiloxane.